1. Field of the invention
The present invention relates to a light path circuit apparatus and a ring laser gyro.
2. Description of the Related Art
An angular velocity sensor has applications in many fields such as car navigation, vibration correction of cameras, video games, air planes, rockets and robots and so on. As an angular velocity sensor, a vibration type is conventionally known that lets an object vibrate by piezoelectricity or electrostatic force and calculates the angular velocity by detecting the Coriolis force generated, or an optical fiber gyro or a ring laser gyro that utilizes Sagnac effects.
A vibration type gyro is not suited for detection of absolute angles because the zero point offset is large. Although optical fiber gyros or a ring lasers gyro have high performance, they are not suited to consumer use because of their comparatively large size and high price.
By MEMS technologies, a technology to constitute a light path circuit part of a ring laser gyro using anisotropic etching of a silicon is disclosed in JP3751553B. This technology can easily constitute a light path circuit part with high precision by batch processing so that a smaller sized and lower cost ring laser gyro can be realized.
However, because the technology described in JP3751553B forms a light path circuit on a surface parallel to the substrate, the angular velocity in only one axial direction is detected. When performing angular velocity detection in more than two axial directions, if a light path circuit part described in JP3751553B is used, it is necessary to combine two or more light path circuit parts used for the detection of each of the axial directions and the device thus becomes too large in size. In addition, when combining two light path circuit parts used for angular velocity detection in one axial direction, it is difficult to ensure that the two parts are mutually orthogonal at the time of assembly.